1. Field of the Invention
The invention relates to a terminal used in an electronic circuit unit to be mounted in a vehicle such as an automotive vehicle and connectable to an external circuit via a plurality of wires.
2. Description of the Related Art
Conventionally, many electronic circuit units each including a circuit board incorporated with an electronic circuit and a board connector for connecting wires for external connection to connection conductors on this circuit board are known as electronic circuit units to be mounted in vehicles. Further, a so-called card edge type connector to be mounted on an edge portion of a circuit board is known as a board connector. Such a connector is known, for example, from Japanese Unexamined Patent Publication No. 2008-098064.
As shown in FIG. 8, a card edge connector described in Japanese Unexamined Patent Publication No. 2008-098064 includes a circuit board 110 with connection conductors 111 on an edge part thereof, a board-side housing 120 for housing this circuit board 110, terminals 130 mounted on the tips of wires and connected to the connection conductors 111, and a wire-side housing 140 for housing the terminals 130. Specifically, each terminal 130 includes a wire connecting portion 131 to be mounted on the tip of the wire and a board connecting portion 132 to be connected to the connection conductor of the circuit board as specifically shown in FIG. 9. The board connecting portion 132 includes a main portion 133 in the form of a rectangular tube, a resilient contact piece 134 integrally formed to this main portion 133 and a biasing member 135 mounted in the main portion 133. The resilient contact piece 134 is shaped to be long in a direction in which the terminal 130 is inserted into the wire-side housing 140 (lateral direction in FIG. 9) and integrally connected to the main portion 133 at a base end portion 134a (left end in FIG. 9) thereof. This resilient contact piece 134 includes a contact portion 134b to be brought into contact with the connection conductor 111 on a side opposite to the base end portion 134a (right side in FIG. 9) thereof. The contact portion 134b of the resilient contact piece 134 is resiliently displaced in a direction (vertical direction in FIG. 9) perpendicular to a longitudinal direction thereof with the base end portion 134a as a supporting point. The main portion 133 includes an opening 133a on the lower surface (lower surface in FIG. 9), and the contact portion 134b projects to the outside of the main portion 133 through this opening 133a. The biasing member 135 is mounted in a compressed state in the main portion 133, and biases the contact portion 134b from the inside to the outside of the main portion 133 by a resilient restoring force thereof. As shown in FIG. 8, in a state where this terminal 130 is inserted in the board-side housing 120 and the contact portion 134b thereof is held in contact with the connection conductor 111, the contact portion 134b is retracted into the main portion 133 against a biasing force of the biasing member 135. In this state, the contact portion 134b is pressed into contact with the connection conductor 111 by a resilient force of the compressed biasing member 135.
The card edge connector described in Japanese Unexamined Patent Publication No. 2008-098064 is mounted in the vehicle, and therefore is subject to a vibromotive force during vehicle running or the like. This may possibly cause the resilient contact piece 134 of the terminal 130 to slightly vibrate with the base end portion 134a thereof as a supporting point. Normally, since the biasing member 135 is biased to press the contact portion 134b into contact with the connection conductor 111, the contact reliability of the contact portion 134b and the connection conductor 111 is not affected even if the resilient contact piece 134 slightly vibrates. However, if a vibration frequency of the vehicle and a natural vibration frequency of the resilient contact piece 134 coincide, the resilient contact piece 134 may resonate and heavily vibrate. In this case, there is a concern about a reduction in the contact reliability of the contact portion 134b and the connection conductor 111 due to a drastic reduction in the contact pressure of the contact portion 134b and the connection conductor 111.
The present invention aims to provide a terminal which is used in an electronic circuit unit and can suppress a reduction in contact reliability even if a resilient contact piece resonates.